Did you ever have a power outage, or do a "dirty" shutdown by pulling the plug? That can cause corruption.
If the restore like Markus suggested doesn't fix it, then I would try removing that one Leviton device as a test. Did this Leviton ever get a firmware update? I think there were some issues that firmware seems to have fixed?
This thread is slightly outdated, but the basic info is good. Maybe you can update yours?
